The KB is http://support.microsoft.com/?kbid=982639 

Download from here http://www.microsoft.com/downloads/details.aspx?FamilyID=09b4973e-3a80-4fb9-9f60-5c6e2b7a2727&displaylang=en

By the way Exchange 2007 SP2 is at Update Rollup 4 : http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=b8f7f872-16d5-49d6-9867-adc01351c06f